1. Field of the Invention
This invention relates in general to systems for detecting persons occupying beds, and in particular to a system for detecting the position and activity level of a body in a bed. Still more particularly, the present invention relates to systems for triggering an alarm under certain conditions relating to a body within a bed.
2. Summary of the Prior Art
Injuries to bed-ridden patients are a major concern the health care and convalescence industries. Bed-ridden patients can be injured by falling out of a bed while in a state of delirium, or by falling while attempting to arise from the bed in a weakened or fatigued state. Therefore, it is useful for nurses or other supervisory personnel to be kept abreast of the activity and position of a patient or person lying in a bed. The ability to monitor remotely a patient's position and activity level in a bed permits closer and more careful supervision of that patient.
Many systems and devices are known that detect the presence, activity level, and other vital signs of a patient or person lying upon a bed. Some of these systems employ pressure transducers for the purpose of detecting heartbeat and respiratory rate (U.S. Pat. No. 4,738,264, Apr. 19, 1988, to Orlando). Such systems, however, are complex and incapable of detecting the position of a patient in the bed.
Other systems employ binary electrical switches to detect the presence or absence of a person in a bed (U.S. Pat. No. 4,700,190, Oct. 13, 1987, to Vance). These systems, again, are incapable of detecting and indicating the position or activity level of a patient within a bed.
Still another known system employs a sensor having an array of binary electrical switches within the bed, and employs a microcomputer or microprocessor to detect which of the switches are closed to indicate an impending attempt to rise from the bed by the patient (U.S. Pat. No. 4,633,237, Dec. 30, 1986, to Tucknott et al.) Such a system is overly complex, and subject to malfunction if any single switch in the array malfunctions.
Still other systems employ fluid (pneumatic or hydraulic) sensors to detect the presence of a patient in a bed (U.S. Pat. No. 4,175,263, Nov. 20, 1979, to Triplett et al.; U.S. Pat. No. 4,020,428, Apr. 26, 1977, to Feldl). These systems have bulky sensors, which are uncomfortable for the patient to lie upon. Also, these systems require complicated detection circuitry and are susceptible to malfunction if the fluid-containing sensor is punctured.
It is therefore desirable to provide a simple, low-cost, easily replaceable, and reliable system for detecting the position and activity level of a patient lying upon a bed.